JP2012132650A - Supercritical cycle heat pump device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercritical cycle heat pump device in which adiabatically compressed high pressure refrigerant falls in a supercritical condition, the performance of a heat pump can be improved by cooling fluid to be heated by a radiator, and which can be continuously operated without stopping the heat pump.SOLUTION: In the supercritical cycle heat pump device which has a compressor 1 adiabatically compressing refrigerant 14, the radiator 2 cooling the adiabatically compressed refrigerant 11, an expanding valve 3 for adiabatically expanding the high pressure refrigerant 12 to low pressure, and an evaporator 4 evaporating the refrigerant 13 having adiabatically expanded and having fallen in low pressure and low temperature and in which the adiabatically compressed high pressure refrigerant falls in a supercritical condition, the fluid to be heated which is heated by heat exchange with the refrigerant in the radiator 2 is cooled before introducing the same into the radiator 2.

Description

  The present invention relates to a supercritical cycle heat pump apparatus that uses a refrigerant that can be in a supercritical state equal to or higher than the critical pressure on the high-pressure side of the refrigerant cycle, and operates in a supercritical state at a compressor discharge pressure.

A heat pump system that uses a refrigerant that can be in a supercritical state on the high-pressure side of the refrigerant cycle has a characteristic that can efficiently perform high-temperature heating by operating the compressor discharge pressure in a supercritical state that is higher than the critical pressure. Yes. Conventional fluorocarbon refrigerants can generate high-temperature water and hot air of 80 to 120 ° C., which is approximately 60 ° C., and are used not only in the hot water supply field but also as various drying devices.
1) Patent Document 1 discloses a system for generating hot water and generating hot water using water as a fluid to be heated to supply hot water, and a heat exchanger that exchanges heat with natural water at the outlet of a radiator. And a system in which two heat exchangers that evaporate a refrigerant with cold water are arranged side by side, and switching between heating hot water supply operation and heating hot water supply / cooling operation can be performed by opening and closing valves installed before and after the heat exchanger. .
2) Patent Document 2 discloses a system that uses air as a fluid to be heated, generates hot air and applies it to drying, and introduces a bypass of part of the outside air and exhaust gas and maximizes the COP. A system is disclosed in which the discharge pressure is determined while operating, and the highly efficient operation is always possible.
3) Patent Document 3 describes a system that uses air as a fluid to be heated and circulates, generates hot air and applies it to drying, and switches between a normal drying operation mode and an energy-saving drying mode with simple control. A enabling system is disclosed.
4) Patent Document 4 is a system that uses air as a fluid to be heated to introduce outside air, generates hot air and applies it to drying, and stores a certain amount of working water supplied as a heat source of a heat pump. In addition, a system has been disclosed in which, while being recycled, the temperature is raised by a working dry gas discharged from a dryer, so that the water temperature is always constant, the energy efficiency is high, and stable operation is possible.

International Publication No. 2006-051617 Pamphlet JP 2010-38469 A JP 2010-82113 A JP 2010-196939 A

In order to efficiently operate the heat pump system, there are the following methods for improving COP (Coefficient Of Performance).
(1) Increase the amount of heat generated by the heat pump.
As a means, there are a method of generating a high-temperature heat source by increasing the compressor outlet pressure and a method of recovering to a lower temperature by a radiator. In this case, when the compressor outlet pressure is increased, the amount of generated heat increases, but the power required for the compressor also increases, and therefore, it may not necessarily lead to an improvement in COP. On the other hand, a method of recovering to a lower temperature with a radiator is effective.
(2) Reduce power used for refrigerant compression.
Means include lowering the compressor outlet pressure and increasing the compressor inlet pressure. When the compressor outlet pressure is lowered, the required power is reduced, but the amount of generated heat and the temperature of the high-temperature heat source are also reduced. Therefore, the COP is not necessarily improved and the temperature required for the heated side may not be reached. On the other hand, a method of increasing the compressor inlet pressure is effective. However, it must be below the critical pressure on the low pressure side of the cycle, and when carbon dioxide is used as the refrigerant, the upper limit is approximately 7.5 MPaG. In addition, the heat source fluid temperature needs to be higher than the evaporator evaporation temperature, and a low temperature heat source fluid such as chiller water or winter cooling tower circulation water cannot be used. Also, the heat source fluid outlet temperature must be higher than the evaporator evaporation temperature, the temperature difference between the inlet and outlet cannot be made large, and a large flow rate of the heat source fluid may be required. In many cases, it is not always effective.

In order to perform operation at a high COP point in a heat pump system using a refrigerant that can be in a supercritical state from the above (1) and (2), one condition (limitation) is that the refrigerant cycle low pressure side does not exceed the critical pressure. .
Since the low pressure side inlet operating point of the refrigerant cycle is a point where the outlet refrigerant of the high pressure side radiator is adiabatically expanded, it depends on the refrigerant outlet temperature of the radiator.
When carbon dioxide is used as the refrigerant, it is desirable that the refrigerant outlet temperature of the radiator on the high pressure side of the refrigerant cycle is 50 ° C. or less at maximum, in which case the temperature difference required for heat transfer is 5 ° C. Although the inlet temperature of the heated fluid that is the cooling source is 45 ° C., it is desirable that the refrigerant outlet temperature is 45 ° C. or less at the maximum and the inlet temperature of the heated fluid is 40 ° C. or less in practice.
In addition, the inlet temperature of the fluid to be heated is desirably −40 ° C. or higher. If this is less than −40 ° C., when only the fluid to be heated flows when the operation is stopped, the refrigerant evaporation temperature in the evaporator also becomes less than −40 ° C., the internal pressure falls below atmospheric pressure, and the outside air enters the refrigerant cycle system. It is necessary to make the container airtight completely, and if it leaks, it is necessary to consider the installation of extraction equipment because moisture and air as non-condensable gas will adversely affect it. Occurs. Furthermore, even during operation, it is necessary to increase the pressure above the critical point pressure by adiabatic compression, the compression ratio is excessive, the compression power is very large, and the compressor performance and efficiency are lowered.
In addition, when the heat source fluid is a liquid, there is a problem of freezing. In the case of water, it is at least -5 ° C or higher, and in the case of brine, the temperature is generally -20 ° C or higher although it depends on the type of antifreeze.

When air is used as the fluid to be heated, outside air and indoor or indoor installation air are generally used. The heat pump system is generally installed in a machine room, and when used as a drying device, the room temperature tends to rise particularly. Therefore, a case of sufficiently exceeding 40 ° C. is assumed. In addition, there are cases where the temperature exceeds 40 ° C. even in the open air due to recent warming.
Therefore, when the inlet temperature of the fluid to be heated exceeds 40 ° C., in the conventional technology, it is necessary to stop the apparatus or reduce the low-pressure side pressure of the cycle and operate at a low COP operating point. In fact, there is a problem of device protection, and when the air temperature, which is the inlet temperature of the fluid to be heated, exceeds approximately 40 ° C., a system is adopted that stops the supercritical cycle heat pump device and outputs an alarm or the like.

  Originally, the temperature of the fluid to be heated rises, the heating temperature difference of the fluid to be heated becomes small, and it is sufficient to supply a small amount of heat, and the operation of the device is stopped under the condition that the efficiency is improved. Is occurring. This economic drop in actual operation has become a major obstacle to the introduction of supercritical cycle heat pump equipment.

  In view of the problems of the conventional technology, the present invention provides a compressor that adiabatically compresses a refrigerant, a radiator that cools the adiabatic-compressed refrigerant, an expansion valve that adiabatically expands the high-pressure refrigerant to a low pressure, and adiabatically expands. In a supercritical cycle heat pump device that includes an evaporator that evaporates the refrigerant that has become low pressure and low temperature, and in which the adiabatic compressed high pressure refrigerant is in a supercritical state, the heat pump is cooled by cooling the fluid to be heated that is heated in the radiator It is an object of the present invention to provide a supercritical cycle heat pump apparatus that can improve the performance of the apparatus and that can be operated continuously without stopping the heat pump.

  In order to achieve the above object, a supercritical cycle heat pump apparatus according to the present invention includes a compressor that adiabatically compresses a refrigerant, a radiator that cools the adiabatic-compressed refrigerant, and a high-pressure refrigerant adiabatically expanded to a low pressure. In a supercritical cycle heat pump apparatus comprising an expansion valve and an evaporator for evaporating a refrigerant that has been adiabatically expanded to a low pressure and a low temperature, the heat of the refrigerant in the radiator is a supercritical cycle heat pump device in which the adiabatic compressed high pressure refrigerant is in a supercritical state. The heated fluid heated by the exchange is cooled before being introduced into the radiator.

According to the present invention, the refrigerant cycle uses a refrigerant that can be in a supercritical state on the high pressure side of the refrigerant cycle, compresses the refrigerant to a supercritical state by a compressor, cools the compressed refrigerant by a radiator, The refrigerant is expanded by an expansion valve to a low pressure, and the refrigerant that has been expanded to a low pressure is evaporated by an evaporator. In the evaporator, the refrigerant is evaporated using a heat source fluid. At this time, the heat source fluid is deprived of the latent heat of vaporization by the refrigerant and becomes a low temperature heat source fluid. In the radiator, the refrigerant is cooled to near the inlet temperature of the fluid to be heated. The refrigerant at the outlet of the radiator at this time is desired to be lowered in order to improve the performance of the heat pump, and the temperature of the heated fluid needs to be lowered.
Therefore, in the present invention, the heated fluid is cooled to be a low temperature heated fluid before being introduced into the radiator. By using a low temperature heated fluid as the heated fluid supplied to the radiator, the temperature of the refrigerant can be lowered. Therefore, the refrigerant outlet temperature of the radiator on the refrigerant cycle high pressure side can be cooled to a low temperature, the refrigerant cycle can be operated efficiently, and COP can be improved. Further, by cooling the heated fluid before introducing it into the radiator, it is possible to eliminate the operation stop of the apparatus, enable continuous operation, and increase the operation efficiency.

In a preferred aspect of the present invention, the heated fluid is air or water.
In the present invention, since the fluid to be heated is cooled once, when the fluid to be heated is air, dehumidification is performed at the same time. Therefore, the effectiveness is increased by using the fluid to be heated for drying. When the fluid to be heated is water, hot water can be generated by generating hot water. In the supercritical cycle heat pump apparatus, the fluid to be heated can be heated to a high temperature state of 100 ° C. or higher. Therefore, when water is used as the fluid to be heated, it can be used for generating steam at atmospheric pressure or higher (100 ° C. or higher) .
In the present invention, the fluid to be heated may be a gas fluid other than air or a liquid fluid. In the case of a gas fluid, any gas fluid other than air that is not toxic, explosive, corrosive, or decomposed / denatured may be used. A combustible gas can be used for heating if sufficient operation methods and measures are taken. Further, the fluid to be heated may be a liquid fluid other than water. The liquid fluid is preferably a fluid that is not toxic, corrosive, or decomposed / denatured like a gas fluid, and even a volatile, explosive, or flammable liquid fluid can be used for heating if sufficient operation methods and measures are taken. . Moreover, if a high temperature heating medium (heating medium oil etc.) is used, the high temperature heating medium of 100 degreeC or more can also be obtained.
In the present invention, since the fluid to be heated is cooled once, in the case of a liquid that is cooled and crystallized to re-concentrate the supernatant liquid, cooling crystallization and concentration can be performed at the same time, so the effectiveness increases.

In a preferred aspect of the present invention, the heat source fluid for evaporating the low-pressure and low-temperature refrigerant in the evaporator is chiller water and / or cooling water.
In the present invention, when chiller water (brine) and / or cooling water is used as the heat source fluid, the heat source fluid is used as the cold heat source, and the outlet temperature of the heat source fluid should be as low as possible. In the case of cooling water, since there is a problem of freezing, the evaporation temperature of the refrigerant is preferably at least 0 ° C. or more, but below this, brine containing antifreeze is used. When directly cooling the heat source fluid, a fluid that is not toxic, corrosive, or decomposed / denatured is desirable, but even if it is a volatile, explosive or flammable liquid fluid, it can be used for cooling if sufficient operation methods and measures are taken. it can. However, the heat source fluid outlet temperature must be determined according to the freezing conditions of the heat source liquid fluid.
In the present invention, the heat source fluid may be a gas fluid. In the case of gas fluids, the use of cold energy for air conditioning can be considered, but any gas fluid that is not toxic, explosive, corrosive, or decomposed / denatured other than air may be used. For example, when using nitrogen gas, carbon dioxide, etc. There is also. Inflammable gases can be used for cooling if sufficient operation methods and measures are taken.

In a preferred aspect of the present invention, a precooler is installed on the inlet side of the radiator and the fluid to be heated is cooled by a cold source fluid.
If the temperature of the refrigerant after being cooled by the heated fluid in the radiator is low, the COP of the refrigerant cycle is improved. Therefore, it is more efficient to set the heated fluid temperature low. Therefore, in the present invention, a precooler is installed on the inlet side of the radiator in order to cool the heated fluid and lower the temperature of the heated fluid. A cold source fluid is used as means for cooling the heated fluid in the precooler.

In a preferred aspect of the present invention, a precooler is installed on the inlet side of the radiator, and the heated fluid is cooled by a heat source fluid on the inlet side of the evaporator.
In the present invention, in order to cool the heated fluid and lower the temperature of the heated fluid, a precooler is installed on the inlet side of the radiator, and the inlet of the evaporator is used as a means for cooling the heated fluid in the precooler. The side heat source fluid is used. According to the present invention, there is no need to separately provide a cold source fluid source for cooling the heated fluid.

A preferred aspect of the present invention is characterized in that a part or all of the heated heat source fluid exiting the precooler is returned to the inlet side of the evaporator.
According to the present invention, it is possible to effectively use a heat source fluid as a heat source of a heat pump by returning a part or all of the heat source fluid heated by removing heat from the fluid to be heated in the precooler to the inlet of the evaporator.

In a preferred aspect of the present invention, a precooler is installed on the inlet side of the radiator, and the heated fluid is cooled by a heat source fluid on the outlet side of the evaporator.
In the present invention, in order to cool the heated fluid and lower the temperature of the heated fluid, a precooler is installed on the inlet side of the radiator, and the outlet of the evaporator is used as a means for cooling the heated fluid in the precooler. The side heat source fluid is used. According to the present invention, there is no need to separately provide a cold source fluid source for cooling the heated fluid.

A preferred aspect of the present invention is characterized in that a part or all of the heated heat source fluid exiting the precooler is returned to the inlet side of the evaporator.
According to the present invention, it is possible to effectively use a heat source fluid as a heat source of a heat pump by returning a part or all of the heat source fluid heated by removing heat from the fluid to be heated in the precooler to the inlet of the evaporator.

In a preferred aspect of the present invention, the refrigerant is carbon dioxide.
According to the present invention, the heat pump device using CO ₂ as a refrigerant has a characteristic that high-temperature heating can be efficiently performed by operating in a supercritical state where the discharge pressure of the compressor is equal to or higher than the critical pressure. Therefore, when air is used as the fluid to be heated, the heated air can be used for drying resin, wood, etc., and when water is used as the fluid to be heated, hot water can be used for hot water supply.

In a preferred aspect of the present invention, the inlet temperature of the heated fluid on the inlet side of the radiator is 40 ° C. or lower and −40 ° C. or higher.
According to the present invention, when carbon dioxide is used as the refrigerant, it is desired that the refrigerant outlet temperature of the radiator on the refrigerant cycle high pressure side is 50 ° C. or less at maximum, in which case the temperature difference necessary for heat transfer is increased. In the case of 5 ° C., the inlet temperature of the heated fluid as the cooling source is 45 ° C., but in practice, the refrigerant outlet temperature is 45 ° C. or less at the maximum and the inlet temperature of the heated fluid is 40 ° C. or less. desirable.
In addition, the inlet temperature of the fluid to be heated is desirably −40 ° C. or higher. If this is less than −40 ° C., when only the fluid to be heated flows when the operation is stopped, the refrigerant evaporation temperature in the evaporator also becomes less than −40 ° C., the internal pressure falls below atmospheric pressure, and the outside air enters the refrigerant cycle system. It is necessary to make the container airtight completely, and if it leaks, it is necessary to consider the installation of extraction equipment because moisture and air as non-condensable gas will adversely affect it. Occurs.

In a preferred aspect of the present invention, a means for detecting the temperature of the heated fluid is provided on the inlet side of the radiator, and a flow rate adjustment for adjusting a flow rate of the fluid supplied to the precooler to cool the heated fluid. Means for controlling the flow rate adjusting means to keep the temperature of the heated fluid at a predetermined temperature.
According to the present invention, the low temperature after being cooled in the precooler by adjusting the flow rate of the cooling fluid supplied to the precooler to cool the heated fluid in response to the temperature change of the heated fluid. The temperature of the fluid to be heated can be kept constant.

The present invention has the following effects.
(1) The radiator outlet temperature of the refrigerant cycle is desirably low in order to improve the COP of the heat pump system. When using a refrigerant that can be in a supercritical state on the high-pressure side of the refrigerant cycle, it may be impossible to evaporate the refrigerant in the evaporator if the outlet temperature of the radiator is higher than a predetermined temperature, and the pressure resistance of the container due to the high temperature It was necessary to limit operation due to limitations. In the present invention, by cooling the heated fluid heated in the radiator before introducing it into the radiator, the performance of the heat pump can be improved, and continuous operation can be performed without stopping the heat pump. Can be raised.
(2) A cold source fluid is used as a means for cooling the heated fluid in the precooler, and the heated fluid is cooled by the cold source fluid in the precooler and becomes a low temperature heated fluid. The temperature of the refrigerant on the outlet side of the radiator can be lowered by lowering the temperature of the heated fluid used for cooling in the radiator. As a result, the amount of generated heat (kW), which is a value obtained by multiplying the specific enthalpy difference (kJ / kg) between the refrigerant on the radiator inlet side and the refrigerant on the outlet side by the refrigerant circulation amount (kg / s) increases, and the evaporator inlet The amount of generated cold heat (kW), which is a value obtained by multiplying the specific enthalpy difference (kJ / kg) between the refrigerant on the outlet side and the refrigerant on the outlet side by the refrigerant circulation amount (kg / s), can also be increased. Therefore, the COP of the refrigerant cycle can be improved.
(3) If the fluid to be heated is cooled by a low-temperature heat source fluid that is used as a heat source in the evaporator and has been deprived of the latent heat energy of evaporation by the refrigerant and the temperature is lowered, the amount of heat generated by the heat pump is used. Heat requirements will not increase. It is also possible to use a heat source fluid that has taken heat from the fluid to be heated by the precooler as a heat source fluid for evaporating the refrigerant in the evaporator. As a result, the heat pump system can be operated efficiently and the COP can be improved.
(4) A sensor for detecting the temperature is installed in the low-temperature heated fluid part cooled by the precooler, and the flow rate of the cold heat source fluid is adjusted so that the temperature of the low-temperature heated fluid becomes the target set temperature. Thus, the temperature of the low-temperature heated fluid can be kept constant with respect to the temperature change of the heated fluid, and stable operation can be performed without being affected by the inlet temperature fluctuation of the cold heat source fluid.
(5) Even if the temperature of the heated fluid changes, the temperature of the low temperature heated fluid can be kept constant, the heat pump system can always be operated efficiently, and the temperature of the heated fluid is the upper limit temperature of the apparatus Even in the case of exceeding the above, continuous operation is possible without stopping the heat pump system, and efficiency reduction due to the stop can be avoided.

FIG. 1 is a system diagram showing an embodiment of the supercritical cycle heat pump apparatus of the present invention. FIG. 2 is a system diagram showing another embodiment of the supercritical cycle heat pump apparatus of the present invention. FIG. 3 is a system diagram showing still another embodiment of the supercritical cycle heat pump apparatus of the present invention. FIG. 4 is a pressure-enthalpy diagram.

Hereinafter, an embodiment of a supercritical cycle heat pump apparatus according to the present invention will be described with reference to FIGS. 1 to 4, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted. In the present embodiment, a case where carbon dioxide (CO ₂ ) is used as a refrigerant that can be in a supercritical state on the high pressure side of the refrigerant cycle will be described. Other refrigerants other than carbon dioxide may be used as long as the supercritical state is reached on the high pressure side of the refrigerant cycle.

FIG. 1 is a system diagram showing an embodiment of the supercritical cycle heat pump apparatus of the present invention.
As shown in FIG. 1, the supercritical cycle heat pump apparatus includes a compressor 1 that adiabatically compresses refrigerant to a supercritical state, a radiator 2 that cools the adiabatic-compressed refrigerant, and a high-pressure refrigerant adiabatically expanded to a low pressure. An expansion valve 3 which is a means for causing the refrigerant to evaporate a refrigerant which has been adiabatically expanded to a low pressure and a low temperature, and a precooler 5 which cools the heated fluid before introducing the heated fluid into the radiator 2. I have.

In the supercritical cycle heat pump apparatus configured as shown in FIG. 1, the refrigerant 14 is compressed to a supercritical state by the compressor 1. The temperature of the refrigerant 11 after compression depends on the required specification of the heating object heated by the heat generated by the heat pump system, but when carbon dioxide is used as the refrigerant, it is often used at about 80 to 130 ° C.
The compressed refrigerant 11 is cooled by the radiator 2 to become the refrigerant 12. When the specific enthalpy difference (kJ / kg) between the refrigerant 11 and the refrigerant 12 at this time is multiplied by the refrigerant circulation amount (kg / s), the amount of generated heat (kW) is obtained. The refrigerant 12 becomes the refrigerant 13 by the expansion valve 3 which is a means for expanding the refrigerant at a low pressure, and is heated by the evaporator 4 and returned to the refrigerant 14. A value obtained by multiplying the specific enthalpy difference (kJ / kg) between the refrigerant 13 and the refrigerant 14 at this time by the refrigerant circulation amount (kg / s) is the generated cold heat amount (kW). Therefore, in order to improve the COP of the refrigerant cycle, it is desirable that the temperature of the refrigerant 12 after being cooled by the radiator 2 is low.

The temperature of the refrigerant 12 depends on the radiator inlet temperature of the heated fluid used for cooling in the radiator 2. In this embodiment, air is assumed as the fluid to be heated at this time, but fluid such as water may be used. In the case where carbon dioxide is used as the refrigerant, in order to cool the refrigerant outlet temperature to approximately 50 ° C., which is an indication of the maximum temperature, it is desirable that the heated fluid inlet temperature in the radiator is approximately 40 ° C. or less.
When air is used as the fluid to be heated, outside air or room air is generally introduced. You may circulate the exhaust wind after using the hot air generated by heating the air with the heat radiator 2 for a drying process.

The heat pump system is generally installed in a machine room, and when used as a drying device, the room temperature tends to rise particularly, so there may be a case where the temperature exceeds 40 ° C. In addition, there are cases where the temperature exceeds 40 ° C. even in the open air due to recent warming.
Further, as described above, since the COP of the refrigerant cycle is improved when the temperature of the refrigerant 12 is low, it is more efficient to set the temperature of the fluid to be heated low. Therefore, in the present invention, the precooler 5 is installed to cool the heated fluid and lower the temperature of the heated fluid.

In the embodiment shown in FIG. 1, a cold source fluid 20 is used as means for cooling the heated fluid 8 in the precooler 5. In the precooler 5, the heated fluid 8 is cooled by the cold source fluid 20 and becomes a low temperature heated fluid 9. The temperature of the refrigerant 12 can be lowered by lowering the temperature of the heated fluid used for cooling in the radiator 2.
As a result, the amount of generated heat (kW), which is a value obtained by multiplying the specific enthalpy difference (kJ / kg) between the refrigerant 11 and the refrigerant 12 by the refrigerant circulation amount (kg / s), increases, and the specific enthalpy difference between the refrigerant 13 and the refrigerant 14. The generated cold energy (kW), which is a value obtained by multiplying the refrigerant circulation rate (kg / s) by (kJ / kg), can also be increased. Therefore, the COP of the refrigerant cycle can be improved.

  In FIG. 2 showing another embodiment of the supercritical cycle heat pump apparatus of the present invention, a part of the heat source fluid 6 is used as means for cooling the heated fluid 8 in the precooler 5. The heat source fluid 6 that has been heated from the heated fluid 8 in the precooler 5 can be partly or wholly returned to the inlet of the evaporator 4 to be effectively used as a heat source for the heat pump.

In FIG. 3 showing still another embodiment of the supercritical cycle heat pump apparatus of the present invention, as a means for cooling the heated fluid 8 in the precooler 5, the low temperature heat source in which the latent heat energy of evaporation is deprived by the refrigerant in the evaporator 4. Fluid 7 is used. The low temperature heat source fluid 7 is supplied to the precooler 5 by the booster pump 21. Then, a part or the whole of the low-temperature heat source fluid heated by taking heat from the heated fluid 8 in the precooler 5 can be returned to the inlet of the evaporator 4 to be effectively used as a heat source for the heat pump.
In this case, the low heat source required to change the heated fluid 8 to the low-temperature heated fluid 9 uses the amount of heat generated by the heat pump and the cold heat generated in the evaporator 4 when the temperature of the refrigerant 12 decreases. The amount is increased by the amount of heat necessary to lower the temperature of the refrigerant 12. Thus, the overall heat requirement does not increase.

The refrigerant 12 is expanded to a low pressure by the expansion valve 3 and becomes a refrigerant 13. Although the expansion valve 3 is used as means for expanding the refrigerant, a capillary tube may be used. The refrigerant 13 is evaporated by the heat source fluid 6 in the evaporator 4 and returns to the refrigerant 14.
As the heat source fluid, cooling water, chiller water, or brine is generally used, and the heat source fluid is generally in the range of −20 ° C. to 40 ° C. Cooling water is room-temperature water such as cooling tower water, industrial water, and city water, and chiller water is water at a lower temperature than cooling water and is generally produced by a refrigerator or the like.

  The flow rate of the heat source fluid amount is adjusted so that the temperature difference between the heat source fluid 6 and the low temperature heat source fluid 7 is approximately 5 ° C. In the embodiment shown in FIG. 1, a sensor 15 that detects the temperature is installed in a conduit through which the low-temperature heated fluid 9 flows. Based on the temperature detected by the sensor 15, the flow rate of the cold source fluid is adjusted by controlling the opening degree of the control valve 17 provided in the pipe through which the cold source fluid 20 flows by the temperature controller 16. The temperature of the low-temperature heated fluid 9 is controlled to be the target set temperature. In the example shown in FIGS. 2 and 3, the temperature of the low temperature heated fluid is adjusted to the target set temperature by adjusting the flow rate of the heat source fluid 6 or the low temperature heat source fluid 7 with the sensor 15, the temperature controller 16 and the control valve 17. Control to become. As a result, even if the temperature of the heated fluid 8 changes, the temperature of the low-temperature heated fluid 9 can be kept constant, the heat pump system can always be operated efficiently, and the temperature of the heated fluid Even when the upper limit temperature is exceeded, continuous operation can be performed without stopping the heat pump system.

When carbon dioxide is used as the refrigerant, the upper limit temperature of the fluid to be heated is 40 ° C., and the lower limit temperature is −40 ° C. in order to maintain a positive pressure in the evaporator 4.
A case is assumed in which carbon dioxide is used as the refrigerant, outside air at 40 ° C. is introduced as the fluid to be heated, -5 ° C. brine is used as the heat source fluid, and the temperature is raised to 125 ° C. in the refrigerant cycle. The low-temperature heat source fluid is taken out at -10 ° C.
When the fluid to be heated is not cooled, the temperature of the refrigerant 12 is approximately 45 ° C., and when the cooling is performed, the refrigerant 12 is cooled to approximately 25 ° C. and 5 ° C.

FIG. 4 is a pressure-enthalpy diagram. As shown in FIG. 4, the refrigerant cycle is cycles 1, 2, and 3. In FIG. 4, some straight lines in cycles 1, 2, and 3 should originally be overlapped, but some straight lines are not overlapped so that each cycle can be identified. Table 1 shows the main values in cycles 1, 2, and 3.

In the case of cycle 1, the outside air at 40 ° C. is introduced into the radiator 2 as it is without being cooled.
In the case of cycle 2, the outside air at 40 ° C. is cooled to 25 ° C. by the precooler 5, and therefore the fluid to be heated can be cooled if there is a cooling water of about 20 ° C. as a cooling source.
As shown in FIG. 1, when the cooling source fluid is provided independently for cooling the heated fluid, not only the generated heat amount but also the generated cold heat amount can be improved.
In the case of the cycle 3, the outside air of 40 ° C. is cooled to 5 ° C. by the precooler 5, so that chiller water or brine of about 0 ° C. is required as a cooling heat source, but the COP can be greatly improved. .
As shown in FIG. 3, a low-temperature heat source fluid 7 from which latent heat of evaporation has been removed by the refrigerant in the evaporator 4 that evaporates the refrigerant 13 can also be used for cooling the heated fluid.
The amount of heat used for cooling the heated fluid is the difference between 345 kJ / kg, which is the refrigerant 12 in cycle 1, and 210 kJ / kg, which is the refrigerant 12 in cycle 3. Since the difference between the enthalpy difference 90 kJ / kg between the refrigerant 13 and the refrigerant 14 as the generated amount and the difference between the enthalpy difference 225 kJ / kg between the refrigerant 13 and the refrigerant 14 as the cold heat generation amount in the cycle 3, a new amount of heat is required. And not.
As described above, COP can be significantly improved by cooling the heated fluid before introducing it into the radiator.

  Although the embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention may be implemented in various different forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Expansion valve 4 Evaporator 5 Precooler 6 Heat source fluid 7 Low temperature heat source fluid 8 Heated fluid 9 Low temperature heated fluid 11, 12, 13, 14 Refrigerant 15 Sensor 16 Temperature controller 17 Control valve 20 Cooling heat Source fluid 21 Booster pump

Claims (11)

A compressor that adiabatically compresses the refrigerant, a radiator that cools the adiabatic-compressed refrigerant, an expansion valve that adiabatically expands the high-pressure refrigerant to lower the pressure, and an evaporation that evaporates the refrigerant that has been adiabatically expanded to low pressure and low temperature A supercritical cycle heat pump apparatus in which a high pressure refrigerant adiabatically compressed is in a supercritical state.
A supercritical cycle heat pump apparatus, wherein a heated fluid heated by heat exchange with a refrigerant in the radiator is cooled before being introduced into the radiator.   The supercritical cycle heat pump apparatus according to claim 1, wherein the fluid to be heated is air or water.   The supercritical cycle heat pump apparatus according to claim 1, wherein a heat source fluid for evaporating the low-pressure and low-temperature refrigerant in the evaporator is chiller water and / or cooling water.   The supercritical cycle heat pump apparatus according to claim 1, wherein a precooler is installed on an inlet side of the radiator and the fluid to be heated is cooled by a cold source fluid.   The supercritical cycle heat pump apparatus according to claim 1, wherein a precooler is installed on the inlet side of the radiator, and the heated fluid is cooled by a heat source fluid on the inlet side of the evaporator.   6. The supercritical cycle heat pump device according to claim 5, wherein a part or all of the heated heat source fluid exiting from the precooler is returned to the inlet side of the evaporator.   The supercritical cycle heat pump apparatus according to claim 1, wherein a precooler is installed on the inlet side of the radiator and the fluid to be heated is cooled by a heat source fluid on the outlet side of the evaporator.   8. The supercritical cycle heat pump device according to claim 7, wherein a part or all of the heated heat source fluid exiting from the precooler is returned to the inlet side of the evaporator.   The supercritical cycle heat pump apparatus according to any one of claims 1 to 8, wherein the refrigerant is carbon dioxide.   The supercritical cycle heat pump device according to claim 9, wherein the inlet temperature of the heated fluid on the inlet side of the radiator is 40 ° C or lower and -40 ° C or higher.   A means for detecting the temperature of the heated fluid is provided on the inlet side of the radiator, and a flow rate adjusting means for adjusting the flow rate of the fluid supplied to the precooler for cooling the heated fluid is provided, and the heated 11. The supercritical cycle heat pump apparatus according to claim 10, wherein the flow rate adjusting means is controlled so as to keep the temperature of the fluid at a predetermined temperature.

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